Gasol was examined by foot specialist Dr. Kenneth Jung on Thursday in Los Angeles, and he confirmed the injury, which originally was diagnosed Wednesday after an MRI.
The Lakers aren't sure whether Gasol will need surgery, sources told ESPNLosAngeles.com.
Gasol tweeted that he's "hoping to recover asap so I can be back with the team and keep fighting until the end of the season. #GoLakers #AlwaysPositive"
Gasol was injured in Tuesday night's win over the Brooklyn Nets.
"I tweaked my fascia in the first half, so I was dealing with quite a bit of soreness in the second half," Gasol said after the game. "So I couldn't do certain things.
"I was dealing with it, but that play when I tried to jump off of it and try go block the shot (by Brooklyn's Brook Lopez), just as I took off, I felt a pop in the bottom of my foot on my fascia and I couldn't get up. I'm worried about it."
Gasol initially tried to play through the injury, which occured with 3:50 left in Tuesday's game. But after one trip up and down the floor, he asked coach Mike D'Antoni for a sub and went to the locker room with Lakers trainer Gary Vitti.
"It felt kind of OK a little bit putting my weight on it without walking or running, but once I started running, I was limping and it was really sore," Gasol said Tuesday. "Even if I tried, I couldn't go."
Gasol finished with 15 points, four rebounds and two blocks in the Lakers' 92-83 win.
The Lakers were granted a disabled player's exception for Jordan Hill last week after the backup center went out with season-ending hip surgery. The exception will allow the Lakers to spend a little more than half of Hill's salary, about $1.78 million, in order to sign a free agent or to absorb a player's contract acquired in a trade.
Despite Gasol's foot injury, the Lakers are not dead set on using the exception, a team source told ESPNLosAngeles.com, and they are hopeful the situation will prompt Dwight Howard to return and play through his sore right shoulder "sooner than later."
The Lakers have won three straight after starting their seven-game trip with a loss to Phoenix, and six of seven overall entering Thursday night's game against the Celtics. But they will face an uphill battle to finish off the trip without Gasol and potentially Howard.
Gasol already has missed 13 games this season because of tendinitis in both knees and a concussion.
"We'll see what happens," D'Antoni told the "Mason & Ireland Show" on ESPNLA 710 radio Wednesday. "Hopefully, Dwight will be back fairly soon, but you approach it like any other game. Guys got to step up.
"We'll play with Robert Sacre. We'll play smaller most of the time. We'll have Metta (World Peace) back (from a one-game suspension). So, we still have enough pieces to win games. That's what we have to do.
"We just got to keep winning and give us a chance to get into the playoffs, then hopefully, we'll have everybody healthy at that point. But all these games are going to be attacked like they're playoff games, and whoever is available is going to have to play well."
ESPNLosAngeles.com's Dave McMenamin and Ramona Shelburne contributed to this report.